perf build: Fix build feature-dwarf_getlocations fail for old libdw

For libdw versions below 0.177, need to link libdl.a in addition to
libbebl.a during static compilation, otherwise
feature-dwarf_getlocations compilation will fail.

Before:

  $ make LDFLAGS=-static
    BUILD:   Doing 'make -j20' parallel build
  <SNIP>
  Makefile.config:483: Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157
  <SNIP>

  $ cat ../build/feature/test-dwarf_getlocations.make.output
  /usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libebl.a(eblclosebackend.o): in function `ebl_closebackend':
  (.text+0x20): undefined reference to `dlclose'
  collect2: error: ld returned 1 exit status

After:

  $ make LDFLAGS=-static
  <SNIP>
    Auto-detecting system features:
  ...                                   dwarf: [ on  ]
  <SNIP>

    $ ./perf probe
   Usage: perf probe [<options>] 'PROBEDEF' ['PROBEDEF' ...]
      or: perf probe [<options>] --add 'PROBEDEF' [--add 'PROBEDEF' ...]
      or: perf probe [<options>] --del '[GROUP:]EVENT' ...
      or: perf probe --list [GROUP:]EVENT ...
  <SNIP>

Fixes: 536661d ("perf: build: Only link libebl.a for old libdw")
Reviewed-by: Leo Yan <[email protected]>
Signed-off-by: Yang Jihong <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Leo Yan <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/build/feature/Makefile

@@ -181,6 +181,9 @@ ifeq ($(findstring -static,${LDFLAGS}),-static)
   ifeq ($(shell test $(LIBDW_VERSION_2) -lt 177; echo $$?),0)
     DWARFLIBS += -lebl
   endif
+
+  # Must put -ldl after -lebl for dependency
+  DWARFLIBS += -ldl
 endif
 
 $(OUTPUT)test-dwarf.bin:

tools/perf/Makefile.config

@@ -147,7 +147,7 @@ ifdef LIBDW_DIR
 endif
 DWARFLIBS := -ldw
 ifeq ($(findstring -static,${LDFLAGS}),-static)
-  DWARFLIBS += -lelf -ldl -lz -llzma -lbz2 -lzstd
+  DWARFLIBS += -lelf -lz -llzma -lbz2 -lzstd
 
   LIBDW_VERSION := $(shell $(PKG_CONFIG) --modversion libdw).0.0
   LIBDW_VERSION_1 := $(word 1, $(subst ., ,$(LIBDW_VERSION)))
@@ -158,6 +158,9 @@ ifeq ($(findstring -static,${LDFLAGS}),-static)
   ifeq ($(shell test $(LIBDW_VERSION_2) -lt 177; echo $$?),0)
     DWARFLIBS += -lebl
   endif
+
+  # Must put -ldl after -lebl for dependency
+  DWARFLIBS += -ldl
 endif
 FEATURE_CHECK_CFLAGS-libdw-dwarf-unwind := $(LIBDW_CFLAGS)
 FEATURE_CHECK_LDFLAGS-libdw-dwarf-unwind := $(LIBDW_LDFLAGS) $(DWARFLIBS)